Multilayer porous film, separator for batteries, and battery

A multilayer porous film, comprising:

• a coating layer,
• a filler,
• a resin binder, and
• a base layer comprising a porous polyolefin resin film,
• wherein
• said coating layer is laminated on at least one surface of the porous polyolefin resin film of said base layer,
• Du is an average particle diameter of said filler which is disposed downward from an upper surface of said coating layer composing an upper surface of said multilayer porous film and has a thickness within 25% of a thickness of said coating layer,
• Db is an average particle diameter of said filler which is disposed upward from an interface between said coating layer and said base layer and has a thickness within 25% of said thickness of said coating layer,
• a ratio of Db/Du is a value of from 1.2 to 10;
• and
• Du is not more than 0.5 μm.